Ductors



J. M. MERRICK,.Jr. I

Insulator for Electric C0nduct0 rs..

Patented Feb. 23; 1869.

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JOHN M. MERRICK, JR, OF BOSTON, MASSACHUSETTS.

' Letters Patent No. 87,187, dated February 23, 1869.

IMPROVED COMPCSITION-INSULATOR FOR TELEGRAPH AND OTHER ELECTRIC CON- DUCIORS.

The Schedule referred to in these Latte-:5 Patent and makingpart of the name.

To all whom it may concern:

Be it known that I, J ons M. MERRICK, J r., of Boston, in the county of Suifolk, and State of Massachusetts, have invented a new andimproved Insulator for Practical Telegraphy; and I do hereby declare that the following is a full, clear, and exact description thereof.-

The nature of my invention consists in making the non-conducting portion oi. insulators, by which the telegraph-wires are supported upon the poles, and by which the escape of the electric current at the points of support is prevented, of a new and recently-discovered composition of matter, possessing remarkable resistance to conduction, to moisture, and dirt, as well as having the requisite strength and uniformity.

To enable others skilled in the art to understand my invention, I will proceed to describe its construction and operation.

Although I do notclaim any novelty in the configuration. of the insulators made by me, I annex a drawing, to illustrate the manner in which the insulating-portions are attached to the metallic or supporting-portions of the insulator.

In the drawing- Figure 1 represents a View of one form of insulator in perspective, and

Figure 2, a sectional view. 7

In the form of insulator shown'in the drawing, there is represented a spike of metal, provided, at one end, with a hook, for holding the wire, and a screw, of a non-comlucting substance, at the other end, for entering the post, or the wooden attachment by which the insulator is fastened to the post.

The non-conducting material surrounding the metallic spike is represented at A in fig. 2.

' The method of construction which I adopt, and the materials used, are as follows:

The insulating-material' which I use is one for which I have rcceivedLetters Patent, numbered 85,018, and dated December 15, 1868, said material being known in the trade as diatite.

This material is composed, and prepared, and applied, to form the insulator, as follows:

Prepared silica, in the utmost possible state of di- I vision which can be obtained, or, what I prefer, the silicious earth, known as diatom aceous or infusorial deposits, naturally in a state of great division, is mixed with gum-shellac in a dry state, or any similar gum, in equal proportions, by weight.

The mixed material is brought to a-semiplastic state through heat applied to it by means of a steam-stove.

The material is then taken out, and pressed between stean'i-rollcrs, such as are used in rolling India rubber.

It is passed repeatedly through these rollers, until the ingredients are perfectly incorporated.

The compound, while still hot, and in a plast c state, is pressed into a metallic (lie; and upon this material the portion of the spike to be covered with the insu-. lating-material is placed.

The die is so constructed as to give the impression of the desired fOIIh which the exterior of the insulator shall have.

Another die, to make an impression of the other side of the insulator, is placed upon the former die and the material which itcontains.

Both dies are then heated, and placed in a powerful press.

The requisite smoothness is given by the polished surface of the die.

The insulator thus moulded, upon being removed from the die, is found to be perfectly finished for use.

The enveloping-material adheres perfectly to the metallic spike, and the end, spirally grooved, may be screwed into any wooden post or support, without separating the enveloping-n)aterial.

I have described and shown only one form in which the insulating-material above mentioned may be applied.

It may be used without metallic supports, in any desired form, or may form parts of compound insulators.

Having fully described the method of construction of my insulator, and the nature of the material of which the non-conducting portions are made, I will state the peculiar advantages which this insulator possesses, and the novel results from this peculiar application which make it a distinct invention in the art of practical telegraphy.

With the vast and increasii extension of telegraphic lines, the possession of an insulator which approaches perfection is of vital importance.

Improvements apparently slight become important, from the extent to which they may be adopted.

First. The first requisite of an insulator is its resistance to conduct-ion. The material of which it is made should be a relatively bad conductor.

Second. As the resistance of insulators is almost purely a question of surface, and, in insulators similar in other respects, the largest in diameter will conduct the best, it is desirable to have a non-conducting material with suflicient cohesive properties to secure an insulator of the smallest possible diameter consistent with strength.

Third. The insulator should have little afiinity for moisture, or power to attract dampness.

Fourth. The material should not deteriorate at its surface, through age or exposure, so as'to become rough, and therefore liable to retain dirt.

Fifth. It should be cheap.

I claim that my insulator possesses all these requisites to a degree never before attained.

The insulating-qual'ities are given by a gum ranking at the very height of the list of non-conductors, and almost identical with amber or electron, the non-conducting properties of which gave electricity its name.

By the process used in the preparation of diatite, each microscopic particleofdiatomaceous earth orsllex, itself a bad conductor, is coated with the gum, while the complete incorporation of the hard particles of diatoriiaceous earth gives to the diatite a strength found in nomaterial equally resistant to conduction.

I am thus able to make the insulators of the smallest diameter consistent with strength.

This insulator has little ailinity for moisture, as compared with glass insulators, ordinarily used.

its resistance to moisture is illustrated by the wellknown fact that glass supports of apparatus used for experiments in frictional eleci ricity are ordinarily varnished with shellac, to lessen the ailinity for moisture.

My insulator possesses all the adi 'antagcs of those made of vuleanite, hard rubber, or ebonite.

\Vith all the excellences of the insulators last named, they are subject to two objections:

Being composed of India rubber and sulphur, when the rulcanite surrounds and is 'in Contact with a spike or supporting-portion of iron, and when the insulator is exposed to rain, the sulphur combines with the iron, forming a sulphurct oi'iron, which, swelling, causes the envelope of vuleanite to split.

A'nofher well-known objection to the use ofvuleanite, hard rubber, or ebonite, under all which nzunes this material is known, is that, by exposure, its snrihee becomes rough and spongy, so as to retain dirt, and therefore will not give a high insulation for a long period.

pressed in dies, is the s'l'noothness and hardness of its surlhce, v.'hich continues under exposure.

The application oi'a material possessing these essential properties to insulators, constitutes the essence of my invention.

\Vhat I claim as my invention, and desire to secure by Letters Patent, is-- An insulator for practical telegraphy, the portions of which, adapted to resist conduction, are composed of a material consisting of a combination of a powder of silica, chemically prepared, or occurring, in the form ot'diatonmceous or infusorialearth, with gum-shellac, or other similar gums, the same being moulded and compressed, substantially as described.

- JOHN M. MERRIUK, JR.

XVitnesses:

J on L. HAYES, FRANCIS S. DYER. 

